This looks like a really nifty idea for those of you with youngsters in your lives (however many generations out).
http://www.popularwoodworking.com/wo...d-block-system

The referenced patent has a rough plan of the individual blocks and an example of usage
http://www.popularwoodworking.com/wp...ds/US61721.pdf

Should be fairly quick to knock out of some scrap if you have a decent finger jointing setup.